Haskell Platform Proposal: add transformers and revise the mtl package to depend on it

Felipe Lessa felipe.lessa at gmail.com
Thu Sep 16 10:30:52 EDT 2010

On Thu, Sep 16, 2010 at 11:21 AM, Duncan Coutts
<duncan.coutts at googlemail.com> wrote:
> It's true that the naming scheme would be more consistent, however I
> think the more important point is to communicate clearly to users of
> the platform what it is that they need to do.
> Consider some Haskell programmer who is not reading this mailing list.
> They use the platform and mtl-1 in their code. If the next HP release
> contains mtl-2 then it is clear to them what they need to do: they
> just need to test their code against mtl-2 (fixing any compilation
> problems and adjusting build-depends version constraints). If on the
> other hand we removed mtl-1 from the platform then our example coder
> does not know what to do. It's much more work for them to discover
> that this new package monads-fd was just added to the platform and it
> seems to provide the same modules.

This is probably the last chance we have to deprecate the name 'mtl'.
Is it doable to:

- Add both mtl-2 and monads-fd to HP.

- Instead of renaming monads-fd to mtl, re-export all monads-fd
modules in mtl-2.

- Mark all mtl-2 modules as deprecated and point to monads-fd.

- After some time, remove mtl-2 from HP.

Packages will still work as with OP's proposal, albeit printing many
deprecation warnings.

Cheers! =)


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